Automatic focusing system for use with a motion picture camera

ABSTRACT

An automatic focusing system has an automatic parallax correction for use with a camera, which is either a motion picture camera or a video camera. The camera includes a variable focus lens and an adjusting mechanism of a lens focus barrel which adjusts the variable focus lens so that an image of a photographic subject is in focus on a focal plane. A pan/tilt head is mounted on a tripod. The automatic focusing system includes a plate, a motorized turntable, a housing and a range finder. The plate is mounted on the pan/tilt head. The camera is mounted on the plate. The motorized turntable is also mounted on the plate. The motorized turntable is servo controlled. The motorized turntable is disposed a fixed and known first distance from the camera and is made to rotate along an axis parallel to the pan-axis of the pan/tilt head. The housing is mounted on the motorized turntable. The range finder is disposed in and mechanically coupled to the housing. The range finder determines a second distance to the photographic subject from the housing.

This application is a continuation-in-part of an application filed Jan.17, 1990 under Ser. No. 466,223.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automatic focusing system for usewith a camera and more particularly to an automatic focusing systemwhich utilizes a laser range finder in order to obtain automaticparallax correction.

2. Description of the Prior Art

Proper focusing of a motion picture camera is of critical importance inthe commercial production of motion pictures. Sharpness of focus is animportant consideration in the production of realistic commerciallyvaluable films. Maintenance of a sharply focused image of the principalobject of interest in a given scene, particularly when the principalobject is in movement toward or from the camera, is a challenging matterin cinematography.

The concept of depth of field is a description of the range of distancesan object of interest can be from the motion picture camera and stillremain in acceptably sharp focus without adjustment of the camera lens.The depth of field becomes smaller with increasing lens focal length,with larger lens aperture and with decreasing object distance to themotion picture camera. There is a tendency in commercial camera workwith a film or video camera toward a long focal length lens which isoperated with a large aperture and at a close distance thereby producinga narrow limit on the depth of field. Under this narrow limit a preciseand accurate adjustment of the lens focus is necessary. Previously acamera operator has depended on his skill to precisely and accuratelyadjust the lens focus.

U.S. Pat. No. 4,534,629, entitled Motion Picture Camera AutomaticFocusing System, issued to Robert W. Bogle and Gary Gero on Aug. 13,1985, and U.S. Pat. No. 4,601,557, entitled Motion Picture CameraAutomatic Focusing System, issued to Robert W. Bogle and Gary Gero onJuly 22, 1986, teach an automatic focusing system for variable focuslens of a motion picture camera which includes a pulse modulator and amicrowave transmitter which is mounted on a camera frame for generatinga high frequency pulsed signal which is transmitted to a selected targetwhich carries a reactive signal generator which is responsive to thefirst signal for coding and retransmitting the coded signal back to areceiver which is mounted on the camera frame, a signal processor fordetermining the interval of travel of the signal and translating theinterval into a distance-analog signal that is transmitted to a focusingmotor for driving the focusing mechanism of the lens for focusing thelens at the distance which is determined by the signal. The automaticfocusing system is mounted on the housing of the motion picture camera.

U.S. Pat. No. 4,371,240, entitled Motion Picture Camera Having anAuto-Focus Adjusting Device, issued to Ichiro Shimizu, Yoshio Komine andMakoto Masunaga on Feb. 1, 1983, teaches an automatic focusing systemfor a motion picurte camera which includes a servo motor with a shaft, amotor gear which is fixedly coupled to the shaft and a lens gear whichis fixedly coupled to a lens barrel of a variable lens system and whichengages the motor gear.

U.S. Pat. No. 4,611,244, entitled Auto-Focus System for Video Camera,issued to Kentaro Hanma and Toshio Murakami on Sept. 9, 1986, teaches anauto-focus system for a video camera having a zooming function. There isa discussion regarding the sufficiency of automatic focusing system fordistances less than one meter. U.S. Pat. No. 4,191,460, entitled Camerawith Automatic Focus Adjustment Device, issued to Makoto Fujiki on Mar.4, 1980, teaches a camera having a zoom lens with a focusing rangechangeover device for selectively permitting photography in either oneof ordinary zoom and macro-zoom modes. U.S. Pat. No. 4,719,485, entitledAutomatic Follow-up Device for Camera, issued to Masao Shikaumi on July12, 1988, teaches an automatic device for a camera which automaticallycaptures a heat source, such as a human being, within a photographingfield on the notion that a moving object to be photographed is often ahuman being.

U.S. Pat. No. 4,351,590, entitled Motion Picture Camera with AutomaticFocusing Device, issued to Noritsugu Hirata, Masamichi Toyama, HidetoIwama, Hidekazu Okajima and Akimasa Nishimura on Sept. 28, 1982, teachesa motion picture camera which has an automatic focusing device.

U.S. Pat. No. 4,294,531, entitled Auto-Focus Movie Camera, issued toEdwin K. Shenk on Oct. 13, 1981, teaches a motion picture camera whichhas a lens mount which is automatically positioned to maintain an imageof a photographic subject in focus on the focal plane by generatingperiodic range pulses having a characteristic directly related tosubject range and converting each pulse to a number which represents thefocus positon of the lens mount.

U.S. Pat. No. Re. 32,138, originally U.S. Pat. No. 4,082,436, entitledMotion Picture Camera, issued to Robert E. Gottschalk on May 6, 1986,teaches in a motion picture camera. U.S. Pat. No. 4,751,540, entiledCamera Tripod, issued to Mark D. Jones on June 14, 1988, teaches atripod which is mounted on a motion picture camera. U.S. Pat. No.3,924,828, entitled Pan, Tilt and Roll Tripod Head, issued to Victor R.Epperson on Dec. 9, 1975, teaches a pan-tilt tripod head with the addedcapability of rolling to either side to provide vertical or horizontalformat for the motion picture camera. A single trigger controls allmotion with the initial trigger squeeze releasing a clamp to allow panand tilt motion and with a further trigger squeeze releasing a frictionlock which allows the head to be rolled to either side. The trigger ismounted on a handle extended from the head for ease of control and theunit is adaptable to standard tripod and camera mounting attachments.

U.S. Pat. No. 4,268,137, entitled Radiation-Emisisve Focussing Systemwith Integration of the Signal Produced by the System's DetectorArrangement, issued to Istvan Cocron, Theodor Huber amd Wolfgang Ruf onMay 19, 1981, teaches an automatic camera focusing system which has atransmitter and two detectors. The transmitter emits two pulses ofradiation to a photographic subject which reflects the pulses ofradiation onto the two detectors which provide a distance measuringsignal to the automatic camera focusing system.

SUMMARY OF THE INVENTION

In view of the foregoing factors and conditions which are characteristicof the prior art it is the primary object of the present invention toprovide an automatic focusing system which utilizes a laser range finderin order to obtain automatic parallax correction.

It is also object of the present invention to provide an automaticfocusing system for a motion picture camera which utilizes thetechniques of a laser radar and triangulation to adjust the lens for thedistance between a moving or standing photographic subject and a camerafocus plane in order to always maintain the photographic subject infocus.

In accordance with the present invention an embodiment of an automaticfocusing system having an automatic parallax correction for use with acamera is described. The camera is either a motion picture camera or avideo camera. The camera includes a variable focus lens and an adjustingmechanism of a lens focus barrel which adjusts the variable focus lensso that an image of a photographic subject is in focus on a focal plane.A pan/tilt head is mounted on a tripod. The automatic focusing systemincludes a plate, a motorized turntable, a housing and a range finder.The plate is mounted on the pan/tilt head. The camera is mounted on theplate. The motorized turntable is also mounted on the plate. Themotorized turntable is servo controlled. The motorized turntable isdisposed a fixed and known first distance from the camera and is made torotate along an axis parallel to the pan-axis of the pan/tilt head. Thehousing is mounted on the motorized turntable. The range finder isdisposed in and mechanically coupled to the housing. The range finderdetermines a second distance to the photographic subject from thehousing.

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims.

Other claims and many of the attendant advantages will be more readilyappreciated as the same becomes better understood by reference to thefollowing detailed description and considered in connection with theaccompanying drawing in which like reference symbols designate likeparts throughout the figures.

DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic drawing of a first automatic focusing system foruse with a motion picture camera which has been constructed inaccordance with the principles of the first embodiment of the presentinvention.

FIG. 2 is a rear elevational view of the first automatic focusing systemof FIG. 1 which includes a range-finding subsystem, an angle-encodingsubsystem, a processing subsystem and a driving assembly.

FIG. 3 is a functional schematic diagram of the range-finding subsystem,the angle-encoding subsystem, the processing subsystem and the drivingassembly of the first automatic focusing system of FIG. 1.

FIG. 4 is a side elevational view in cross-section of the firstautomatic focusing system of FIG. 1.

FIG. 5 is an optical-schematic drawing of the range-finding subsystemand the angle-encoding subsystem of the first automatic focusing systemof FIG. 1.

FIG. 6 is a schematic drawing of a second automatic focusing system foruse with a motion picture camera which has been constructed inaccordance with the principles of the second embodiment of the presentinvention.

FIG. 7 is a top plan view of the second automatic focusing system ofFIG. 6 which includes a range-finding subsystem, a processing subsystemand a driving assembly.

FIG. 8 is a side elevational view in cross-section of the secondautomatic focusing system of FIG. 6.

FIG. 9 is a front elevational view of a remote control module for usewith the second automatic focusing system of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In order to understand the present invention it is necessary to refer tothe following description of its preferred embodiment in conjunctionwith the accompanying drawing. Referring to FIG. 1 in conjunction withFIG. 2 and FIG. 3 a first automatic focusing system 10 is for use with amotion picture camera 15 which is mounted on a first tripod 16. U.S.Pat. No. 3,924,828 teaches a tripod which may be used. The motionpicture camera 15 includes a variable focus lens 17 and an adjustingmechanism 18 for adjusting the position of the variable focus lens 17 sothat an image of a photographic subject is in focus on its focal plane.U.S. Pat. No. 4,294,531 teaches an adjusting mechanism 18 which includesa lens gear 19 which is fixedly coupled to a lens barrel 20 of thevariable focus lens 17, a motor gear 21 which is engagingly coupled tothe lens gear 19 and a servo motor 22 which has a shaft 23. The motorgear 21 is fixedly coupled to the shaft 23. U.S. Pat. Nos. 4,191,460 and4,601,557 also teach adjusting mechanisms.

Referring to FIG. 2 in conjunction with FIG. 3 and FIG. 4 the firstautomatic focusing system 10 includes a laser range-finding subsystem24, an angle-encoding subsystem 25, a processing subsystem 26 and adriving assembly 27. A second tripod 28 has a mounting plate 29. Thefirst automatic focusing system 10 includes a housing 30 which ismounted on the mounting plate 29. The first automatic focusing system 10is disposed apart from the motion picture camera 15 a first distance,L₁, and from the photographic subject a second distance, L₂. The laserrange-finding subsystem 24 and the angle-encoding subsystem 25 aredisposed within and mechanically coupled to the housing 30. The laserrange-finding subsystem 24 determines the first distance, L₁, along afirst line and the second distance, L₂, along a second line and providesa first signal and a second signal which are proportional to the firstand second distances, L₁ and L₂, respectively. The angle encodingsubsystem 25 measures the angle, θ, by which the first and second linesdiverge from each other and provides a third signal which isproportional to the angle, θ. The processing subsystem 26 processes thefirst, second and third signals to determine a third distance, L₃,between the motion picture camera 15 and the photographic subject andthen generates an output signal which correlates to the third distance,L₃.

Referring to FIG. 2 in conjunction with FIG. 3 the adjusting mechanism18 also includes an incremental encoder 31 which is mechanically coupledto the shaft 23. The driving assembly 27 includes a motor controller 32and a servo amplifier 33 which is electrically coupled to the servomotor 22 in order to drive the servo motor 22 in response to the outputsignal. The incremental encoder 31 is electrically coupled to the motorcontroller 32. The incremental encoder 31 measures the angular positionof the shaft 23 and generates a feed-back signal which provides theexact angular position of the shaft 22. The feed-back signal is sent tothe motor controller 32.

Referring to FIG. 2 in conjunction with FIG. 3 and FIG. 5 theangle-encoding subsystem 25 includes a first shaft 34, a firstincremental angle encoder 35 and a first quadrature decoder 36 whichprovides an angle input signal. The first shaft 34 is fixedly coupled tothe mounting plate 29 and rotatively coupled to the housing 30 throughthe first incremental angle encoder 35. U.S. Pat. No. 4,587,513,entitled Noncontact Shaft Angle Detector, issued to David E. Burrowes,Alan W. Holmes and Daniel R. Valentine on May 6, 1986, teaches anapparatus which utilizes a patterned disc which is secured to the shaftin order to non-contactly determine the shaft angle. The disc hassectors of different optical properties so that radiant energy directedto the disc is encoded by the sectored pattern. U.S. Pat. No. 4,129,862,entitled Apparatus for Digitally Encoding the Angular Position of aShaft with Respect to a Reference Bearing, issued to Irving I. Kaplanand Daniel J. Lincoln on Dec. 12, 1978, teaches a high resolutiondigital angle encoder for determining the angle of a shaft with respectto a reference position. U.S. Pat. No. 4,709,146, entitled OpticallyCoupled Shaft Angle Encoder, issued to Harold J. Reitsema on Nov. 24,1987, teaches an optically coupled shaft angle encoder for measuringrelative rotational angle of a shaft. The first automatic focusingsystem 10 also includes a manual input subsystem 37 which includes aknob 38, a second shaft 39, a second incremental angle encoder 40 and asecond quadrature decoder 41 which provides a manual input signal. Thesecond shaft 38 is fixedly coupled to the knob 38 and rotatively coupledto the housing 30 through the second incremental angle encoder 35. Thefirst automatic focusing system 10 is secured to the the mounting plate29 of the second tripod 2 through the incremental angle encoder 35. Thequadrature decoder 36 determines the direction and the angle between thefirst automatic focusing system 10 to motion picture camera 15 line andthe first automatic focusing system 10 to photographic subject line.

Referring to FIG. 3 in conjunction with FIG. 5 the laser range-findingsubsystem 24 includes a laser driver 42, a diode laser 43, a timingmodule 44, an optical receiver 45 and an optical system 46. The opticalreceiver 45 includes an avalanche photo diode detector 47, atransimpedance amplifier 48, an amplifier 49 and a constant fractiondiscriminator 50. The transimpedance amplifier 48 is electricallycoupled to the avalanche photo diode detector 47. The amplifier 49 iselectrically coupled to the transimpedance amplifier 48. The constantfraction discriminator 50 is electrically coupled to the amplifier 49.The diode laser 43 generates and directs a plurality of pulses of lightenergy at either the motion picture camera 15 or the photographicsubject so that the pulses of light energy are reflected back thereby.The light pulse emitted from the diode laser 43 is directed by theoptical system 46 to fall onto the photographic subject. The light whichis reflected by the photographic subject is gathered by the opticalsystem 46 and caused to focus onto the avalanche photo diode detector47. The avalanche photo diode 47 has a sensitivity which closely matchesthe emission wavelength of the diode laser 43 and a gain relative to aPIN diode which is on the order of 500 or more. The current pulsegenerated within the avalanche photo diode 47 in response to thereceived laser pulse is first amplified by the transimpedance amplifier48 which has a bandwidth greater than 1 GHz and is further amplified bythe amplifier 49 which has a wide bandwidth by approximately 30 db. Thepulse from the amplifier 49 is converted to a logic level signal by theconstant fraction discriminator 50. The leading edge of the logic leveloutput of the constant fraction discriminator 50. The leading edge ofthe logic level output rises at a time which is independent of theamplitude of the received light pulse over a large range of receivedamplitudes. The output pulse from the constant fraction discriminator 50is used to halt the time measurement process implemented by the timingmodule 44. The optical receiver 45 receives the reflected pulses oflight energy from either the motion picture camera 15 or thephotographic subject. The timing module 44 measures the elapsed time ofthe roundtrip of the pulses of light energy. The processing subsystem 26determines either the first distance, L₁, or the second distance, L₂,from the elapsed time. U.S. Pat. No. 4,586,806, issued to SeiichiIsogichi and Hiroshi Takahashi on May 6, 1986, teaches an active typecamera range-finder which includes a light-emitting diode, a pluralityof photo-transistors, an amplifier and an operable circuit. Thelight-emitting diode emits light energy to an object. Thephoto-transistors generate electric signals corresponding to the lightenergy which is reflected from the object. The amplifier providesautomatic gain control. The operable circuit generates a distance signalbetween the camera and the object from the electric signals. U.S. Pat.No. 4,561,775, Thermally Integrated Laser/FLIR Rangefinder, issued toThomas R. Patrick, Richard Powell and Barry N. Berdanier on Dec. 31,1985, teaches a laser range-finder which includes a laser transmitter, areceiver and a counting circuit. The laser transmitter directs lightenergy toward a target. The receiver detects the return light energywhich is the light energy which is reflected from the target. Thecounting circuit counts the time between the firing of the lasertransmitter and detection of the return light energy. U.S. Pat. No.4,613,231, entitled Laser Range Finder with Non-Linearity Compensation,issued to Guenter Wichmann on Sept. 23, 1986, also teaches a rangefinder which includes a laser transmitter, a receiver and a countingcircuit. U.S. Pat. No. 4,690,550, entitled Laser Range Finder, issued toChristopher Kuhne on Sept. 1, 1987, teaches a laser range finder whichhas a telescope used for both transmitting and receiving. U.S. Pat. No.4,787,291, entitled Gun Fire Control System, issued to Millard Frohockon Nov. 29, 1988, teaches a laser range finder for use in a gun firecontrol system.

Referring to FIG. 5 in conjunction with FIG. 3 the processing device 24includes a micro-processor 51, an electronically programmable read onlymemory (EPROM) 52, a keyboard 53, an alpha-numeric display and driver54, a light emitting diode (LED) viewfinder display and driver 55 and aviewing optical system 56. The micro-processor 5 has at least five inputterminals and three output terminals. The timing module 44 iselectrically coupled to a first of the five input terminals. Thekeyboard 53 is electrically coupled to a second of the five inputterminals. The first quadrature decoder 36 is electrically coupled to athird of the five input terminals. The second quadrature decoder 41 iselectrically coupled to a fourth of the five input terminals. Theelectronically programmable read only memory 52 is electrically coupledto a fifth of the five input terminals in order to provide a softwareprogram for calculating the equation:

    L.sub.3.sup.2 =L.sub.1.sup.2 +L.sub.2.sup.2 -2L.sub.1 L.sub.2 cos θ.

In the calibration procedure the operator uses the first automaticfocusing system 10 to measure the distance between the focal plane ofthe motion picture camera 15 and itself as well as to establish areference line for measuring the angle, between the first automaticfocusing system 10 and the motion picture camera 15. The adjustingmechanism 18 is able to adjust the position of the variable focus lens17 so that an image of a photographic subject is in focus on the focalplane of the motion picture camera 15. The variable focus lens 17 ischaracterized by its effective focal length and a scaling factor whichrelates how many degrees the lens gear 19 on the adjusting mechanism 18must be rotated for any given distance between the movie picture camera15 and the photographic subject. When an operator confirms that thevariable focus lens 17 is in proper focus at the focal plane of themotion picture camera 15 at each of the specified distances he presses akey on the keyboard 53 to enter the data. The operator of the firstautomatic focusing system 10 is prompted by the alpha-numeric displayand driver 54 to focus the variable focus lens 17 at three points: thefirst point at infinity, the second point at a middle distance and athird point at the closest possible distance. The operator rotates theknob 38 to manually control the position of the variable focus lens 17.Rotation of the knob 38 causes the second quadrature decoder 41 to sendelectronic pulses to the microprocessor 51 which causes the motorcontroller 32 and the servo amplifier 33 to drive the servo motor 22thereby rotating the lens barrel 19 of the variable focus lens 17. Whenthe operator confirms that the variable focus lens 17 is in proper focusat the focal plane of the motion picture camera 15 at each of thespecified distances he presses a key on the keyboard 53 to enter thedata. The microprocessor 51 uses the equation,

    1/f=1/O+1/I,

for the relationship between focal length, f, image distance, I, andobject distance, O, to calculate the effective focus length of thevariable focus lens 17. Furthermore, since the variable focus lens 17 iscustomarily implemented using a threaded screw mechanism, the imagedistance can be expressed in terms of angular rotation, θ, of the lensbarrel 19, a first constant, k, and a second constant, f by theequation,

    I=k×θ+f.

The software routines written in the electronically programmable readonly memory (EPROM) 52 are used to determine the constants, k and f,from lens calibration data.

The first automatic focusing system 10 can now be used to implement anautofocus function. When the operator presses the "focus lock" key onthe keyboard 53 or an auxiliary switch which located on the pan arm ofthe second tripod 29, the microprocessor 51 sends a trigger pulse to thetiming module 44 which converts the TTL level logic pulse to a highcurrent pulse of approximately 15 amperes which causes the diode laser43 to emit a short light pulse. Part of the high current driving pulseis sent to the "start" input of the timing module 44. The digital valueof the time measurement is sent to the microprocessor 51 which dividesthe measured time interval presented by the timing module 44 by thevalue of the speed of light in air to determine the distance between thefirst automatic focusing system 10 and the photographic subject.

The microprocessor 51 uses both the effective focal length of thevariable focus lens 17 and an angular scaling factor both measuredduring the calibration sequence to calculate the proper angle ofrotation for the lens barrel 19. The angular position information issent to the motor controller 32 through one of the input terminals ofthe microprocessor 51. The motor controller 32 compares the actualposition of the lens gear 19 as measured by the incremental encoder 31to the angular position sent to the motor controller 32 from themicroprocessor 51.

The motor controller 51 sends an error signal to the servo amplifier 33which drives the servo motor 22. The shaft 23 turns the motor gear 21and the lens gear 19 on the lens barrel 20 so that the lens gear 19 isat the position specified by the microprocessor 51.

In addition to the fully automatic autofocus function as describedabove, several modes using both the laser ranging data as well as manualdata input has been implemented in this design.

By choosing the manual offset mode from keyboard 53 the operator cancause the lens to focus at a point either closer or farther than thephotographic subject by using the knob 38. In this mode of operation theamount of offset introduced manually is shown in the alpha-numericdisplay and driver 54 and the light emitting (LED) viewfinder displayand driver 55 indicating to the operator where the variable focus lens17 is focused relative to the photographic subject.

By choosing the focus split mode from the keyboard 53 the operator canmanually control the rate at which the variable focus lens 17 changesfocus from one photographic subject to a second photographic subject. Inthis mode the operator uses the "focus lock" button to cause thevariable focus lens 17 to focus to a first photographic subject. He thenreleases the "focus lock" button and centers the crosshair in the lightemitting diode (LED) viewfinder display and driver 55 on a secondphotographic subject. The alpha-numeric display and driver 54 and thelight emitting diode (LED) viewfinder display and driver 55 indicate thedistance between the first and second photographic subjects. The servomotor 22 will remain on the first photographic subject until the knob 38is rotated to bring focus onto the second photographic subject. As thefocus is shifted between the two photographic subjects, the lightemitting diode (LED) viewfinder display and driver 55 indicates theoffset between the variable focus lens 17 and the second photographicsubject. When the light emitting diode (LED) viewfinder display anddriver 55 indicates zero the lens will be focused on the secondphotographic subject.

In order to prevent the variable lens 17 from being focused to infinitywhen the operator misses the photographic subject or focused to anobstructing object which is interposed between the photographic subjectand the first automatic focusing system 10. The microprocessor 51 can begiven a near focus limit and a far focus limit through the knob 38.Objects which are measured to be outside range specified by these focuslimits will be ignored, and the focus will remain unchanged until avalid measurement within the desired range is made.

Referring to FIG. 5 the diode laser 43, the optical receiver 45 and theviewing optical system 56 are all aligned along the same line of sight.The diode laser 43 generates and directs a laser light pulse which iscollimated by a laser collimating lens 57 and which passes through acentral elliptical hole 58 in a beam-splitter 59. A negative lens 60 andan objective lens 61 form a beam expander. An infrared mirror 62reflects the laser light pulse which has been diverged after passingthrough the negative lens 60. The objective lens 61 recollimates thelaser light pulse. The objective lens 61 converges the laser light whichhas been reflected from the photographic subject. The infrared lasercomponent of this light is reflected by the infrared mirror 62 throughthe negative lens 60 which recollimates this light. The beam-spitter 59reflects the infrared light through a narrow band interference filter 63which reduces the amount of ambient light which tends to obscure theweak reflection signals. A detector lens 64 focuses the collimated lightonto the avalanche photo diode detector 47 of the optical receiver 45.Visible light is converged by the objective lens 61 and passes throughthe infrared mirror 62 and is imaged onto a ground glass/crosshair/fieldoptical lens 65. A roof penta-prism 66 reverts the image which is viewedthrough an eye-lens 67. One side of the penta-prism 66 has an unsilveredwindow 68 which allows the light emitting diode (LED) viewfinder display55 to be viewed through the penta-prism 66 and the negative lens 60.

Referring to FIG. 6 in conjunction with FIG. 7 a second automaticfocusing system 110 has an automatic parallax correction for use with acamera 111, which is either a motion picture camera or a video camera.The camera 111 includes a variable focus lens and an adjusting mechanismof a lens focus barrel which adjusts the variable focus lens so that animage of a photographic subject is in focus on a focal plane. A pan/tilthead 112 is mounted on a tripod 113. The second automatic focusingsystem 110 includes a plate 121, a motorized turntable 122, a housing123 and a range finder 124. The plate 121 is mounted on the pan/tilthead 112. The camera is mounted on the plate 121. The motorizedturntable 122 is also mounted on the plate 121. The motorized turntable122 is servo controlled. The motorized turntable 122 is disposed a fixedand known first distance from the camera 111 and is made to rotate alongan axis parallel to the pan-axis of the pan/tilt head 112. The housing123 is mounted on the motorized turntable 122. The range finder 124 isdisposed in and mechanically coupled to the housing 123. The rangefinder 124 determines a second distance to the photographic subject fromthe housing 123.

Referring to FIG. 8 in conjunction with FIG. 5 and FIG. 9 the secondautomatic focusing system 110 also includes a microprocessor 131, adriving mechanism 132 and a rotating mechanism 133. The microprocessor131 processes the first and second distances to generate an outputsignal which correlates to the required angle of rotation for themotorized turntable. The driving mechanims 132 drives the adjustingmechanism of the lens focus barrel. The rotating mechanism 133 rotatesthe motorized turntable 12 in accordance with the output signal of themicro-processor. A second automatic focusing system 110 may also haveoperator-directed steering for choice of focus target by includingtransducer 141, a video camera 142, a video monitor 143. The transducer141 generates an electrical signal representing the angle of rotationabout the pan-axis of the housing 123 relative to the camera 111required by operator. The video camera 142 views the line of sight ofthe range finder 124. The video monitor 143 remotely displays the imagewhich the video camera 142 generates. The second automatic focusingsystem 110 adjusts the variable focus so that an image of a photographicsubject is in focus on a focal plane. A remote control module 151remotely controls the second automatic focusing system 110 so that anoperator can pan the line of sight of the second automatic focusingsystem 110 relative to its line of sight. The second automatic focusingsystem 110 may also have operator-directed steering for choice of focustarget by an electro-mechanical steering mechanism 161 and thetransducer 141. The electro-mechanical steering mechanism 161 steers theline of sight of the range finder 124. The transducer 141 generates anelectrical signal representing the angle of rotation about the pan-axisof the line of sight of the range finder 124 relative to the camera 111required by operator. The video camera 142 views the line of sight ofthe range finder 124. An electronic generator 162 generates a videosignal representing a rectile target whose position on the video displaymonitor 143 is correlated to an electrical signal to coincide with theline of sight of the range finder 124. An electronic combining circuit163 combines the video rectile target signal and the video signal whichrepresents the line of sight of the range finder 124. The video monitor143 remotely displays the combined images generated by the video camera142 and the recticle target so that an image of a photographic subjectis in focus on a focal plane.

From the foregoing it can be seen that an automatic focusing system foruse with a camera has been described. It should be noted that thesketches are not drawn to scale and that distance of and between thefigures are not to be considered significant.

Accordingly it is intended that the foregoing disclosure and showingmade in the drawing shall be considered only as an illustration of theprinciples of the present invention.

What is claimed is:
 1. An automatic focusing system for use with amotion picture camera which is mounted on a first tripod and whichincludes a variable focus lens and an adjusting mechanism for adjustingthe variable focus lens so that an image of a photographic subject is infocus on a focal plane, said automatic focusing system comprising:a. ahousing which is mounted on a second tripod which is disposed apart fromthe motion picture camera a first distance and from the photographicsubject a second distance; b. range-finding means for determining saidfirst distance along a first line and said second distance along asecond line and for providing a first signal and a second signal whichare proportional to said first and second distances, respectively, saidrange-finding means being mechanically coupled to said housing; c.angle-measuring means for measuring said angle by which said first andsecond lines diverge from each other and for providing a third signalwhich is proportional to said angle, said angle-measuring means beingmechanically coupled to said housing; d. processing means for processingsaid first, second and third signals to determine a third distancebetween the motion picture camera and the photographic subject andgenerating an output signal which correlates to said third distance; ande. driving means for driving the adjusting mechanism in response to saidoutput signal.
 2. An automatic focusing system according to claim 1wherein said range-finding means is a laser range finder whichcomprises:a. a laser which generates and directs a plurality of pulsesof light energy at a target so that the pulses of light energy arereflected by the target; b. an optical receiver which receives thereflected pulses of light energy from the target; c. time-measuringmeans for measuring the elapsed time of a roundtrip of the pulses oflight energy; and d. processing means for determining the distancebetween the target and said range finder.
 3. An automatic focusingsystem with automatic parallax correction for use with a camera which ismounted together with the camera on a common pan/tilt head, which ismounted on a tripod, and which includes a variable focus lens and anadjusting mechanism of a lens focus barrel for adjusting the variablefocus lens so that an image of a photographic subject is in focus on afocal plane, said automatic focusing system comprising:a. a plate whichis mounted on the pan/tilt head and on which the camera is mounted; b. amotorized turntable which is mounted on said plate and which is servocontrolled, said motorized turntable being disposed a fixed and knownfirst distance from the camera and being made to rotate along an axisparallel to the pan-axis of the pan/tilt head; c. a housing which ismounted on said motorized turntable; d. ranging finding means fordetermining a second distance to the photographic subject from saidhousing, said range finding means being disposed in and mechanicallycoupled to said housing; e. processing means for processing the firstand second distances to generate an output signal which correlates tothe required angle of rotation for said motorized turntable; f. drivingmeans for driving the adjusting mechanism of the lens focus barrel; andg. rotating means for rotating said motorized turntable in accordancewith the output signal of said processing means.
 4. An automaticfocusing system with both automatic parallax correction andoperator-directed steering for choice of focus target for use with acamera which is mounted together with the camera on a common pan/tilthead, which is mounted on a tripod, and which includes a variable focuslens and an adjusting mechanism of a lens focus barrel, said automaticfocusing system comprising:a. a plate which is mounted on the pan/tilthead and on which the camera is mounted; b. a motorized turntable whichis mounted on said plate and which is servo controlled, said motorizedturntable being disposed a fixed and known first distance from thecamera and made to rotate along an axis parallel to the pan-axis of thepan/tilt head; c. a housing which is mounted on said motorizedturntable; d. range finding means for determining a second distance tothe photographic subject from said housing, said range finding meansbeing disposed in and mechanically coupled to said housing; e. atransducer which generates an electrical signal representing the angleof rotation about the pan-axis of said housing relative to the camerarequired by operator; f. processing means for processing the first andsecond distances and said electrical signal to generate an output signalwhich correlates to the required angle of rotation for said motorizedturntable; g. driving means for driving the adjusting mechanism of thelens focus barrel; h. rotating means for rotating said motorizedturntable in accordance with the output signal of said processing means;i. a video camera which views the line of sight of said range findingmeans. j. a video monitor which remotely displays the image which saidvideo camera generates whereby said automatic focusing system adjuststhe variable focus so that an image of a photographic subject is infocus on a focal plane; and k. a remote control module which remotelycontrols said automatic focusing system so that an operator can pan theline of sight of said automatic focusing system relative to the line ofsight of said automatic focusing system.
 5. An automatic focusing systemwith both automatic parallax correction and operator directed steeringfor choice of focus target for use with a camera which is mountedtogether with the camera on a common pan/tilt head, which is mounted ona tripod, and which includes a variable focus lens and an adjustingmechanism of a lens focus barrel for adjusting the variable focus lens,said automatic focusing system comprising:a. a plate which is mounted onthe pan/tilt head and on which the camera is mounted; b. a housing ismounted on said plate; c. range finding means for determining a seconddistance to the photographic subject from said housing, said rangefinding means being disposed in and mechanically coupled to saidhousing; d. electro-mechanical steering means for steering the line ofsight of said range finding means; e. a transducer which generates anelectrical signal representing the angle of rotation about the pan-axisof the line of sight of said range finding means relative to said camerarequired by operator; f. processing means for processing the first andsecond distances and said electrical signal to generate an output signalwhich correlates to the required angles of rotation of the lens focusbarrel and the angle of rotation for the line of sight of said rangefinding means; g. driving means for driving the adjusting mechanism ofthe lens focus barrel; h. rotating means for rotating theelectro-optical means to steer the line of sight of said range findingmeans in accordance with output signal of said processor means; i. avideo camera which views the line of sight of said range finding means;j. electronic generating means for generating a video signalrepresenting a rectile target whose position on said video displaymonitor is correlated to said third electrical signal to coincide withthe line of sight of said range finding means; k. electronic combiningmeans for combining said video rectile target signal and said videosignal which represents the line of sight of said range finding means;l. a video monitor which remotely displays the combined images generatedby said video camera and said recticle target whereby an image of aphotographic subject is in focus on a focal plane; and m. a remotecontrol module which remotely controls said automatic focusing system sothat an operator can pan the line of sight of said automatic focusingsystem relative to the line of sight of said automatic focusing system.